1. Field
The present invention relates to a method and apparatus for controlling a disk drive servo, and more particularly, a method and apparatus for controlling a focus servo of an optical disk drive.
2. Description of the Related Art
Optical disks, which are used as recording media of optical disk drives, can be classified as compact discs (CDs), digital versatile discs (DVDs), and next-generation discs such as Blue-ray discs (BDs) and high-density DVDs (HD DVDs). Data is recorded to and reproduced from BDs using a blue laser having a short wavelength, and thus BDs have a drastically increased storage capacity compared with DVDs.
In order to record data to or reproduce data from an optical disk, an optical disk drive needs to perform focus servo control so that a beam projected by a pickup can be focused on a recording surface of the optical disk. Focus servo control can be roughly divided into a focus pull-in operation and a focus control operation.
In the focus pull-in operation, when a focus servo control loop is turned off, a location of a recording surface on a disk is searched for by moving an objective lens of a pickup toward the top surface of the disk. In the focus control operation, after the recording surface of the disk is found, the focus servo loop is turned on and then the position of the objective lens of the pickup is controlled so that a beam projected by the pickup is accurately focused on the recording surface of the disk.
Korean Patent Publication No. 1991-0008668 discloses a conventional focus pull-in method.
According to a conventional art, when a large level of a signal for determining a point in time at which a focus servo is enabled is generated from a cover layer of a disk, the cover layer of the disk may be misinterpreted as a recording layer thereof, and thus focus servo control may pull in the cover layer of the disk.